1. Field of the Invention
The present invention relates to a plasma etching method and plasma etching apparatus, and more particularly relates to a plasma etching method and plasma etching apparatus that performs an etching process for transferring a fine pattern.
2. Description of the Related Art
In recent years, the shrinking of dimensions for transistors comprising a semiconductor integrated circuit device has made advances in response to demand for high integration, high functionality, and high speed operation in a semiconductor integrated circuit device. In conjunction with this shrinkage, transistors have been developed that provide a metal gate electrode (hereafter referred to as a metal gate) composed of metallic material such as TiN, TaN, TaSiN, or the like; and a gate insulator (hereafter referred to as high-k film) composed of a high dialectic film including a hafnium-based oxide such as HfOx and HfSiOx, or the like. To manufacture a stable fine transistor that provides this type of metal gate and high-k film, a microfabrication technology is necessary that enables the gate material to be processed stably and with high precision.
The fabrication process of this type of metal gate material uses a dry etching apparatus such as a plasma etching apparatus in the same manner as the fabrication process of a gate electrode consisting of conventional polysilicon film. The etching gas used with such dry etching apparatus is a halogen-based gas such as chlorine, and etching can proceed because the metallic material reacts with the plasma of the halogen-based gas to create a metal halide.
In order to be able to process a metal gate stably and with favorable yield rate using this type of dry etching apparatus, particles which are major source of pattern defects must be reduced. In the fabrication process of the metal gate described above, the metal halide is generated at etching process and adheres to the inner surface of the chamber. An adhesiveness of the metal halide is low against the chamber inner surface and easily exfoliates from the chamber inside surface. For this reason, in order to stably fabrication of the metal gate, exfoliation of reaction product adhered to the chamber inner surface that includes the metal halide must be suppressed.
As a technology for preventing the exfoliation of the reaction product having a low adhesiveness with the chamber inner surface, Japanese unexamined patent publication No. 2003-257946 (hereafter referred to as JP2003-257946) discloses the technology in which an adhesive layer is formed on the chamber inner surface in the condition that the chamber inner surface is clean without a reaction product adhered thereon, and etching is performed on a film to be etched in the condition that the adhesive layer has been formed.
For example, with a parallel plate type plasma etching apparatus on which is mounted a wafer for etching at a lower electrode, an adhesive layer is formed at the upper electrode opposing the wafer in a clean chamber condition. Next, the etching process is performed by generating plasma of etching gas supplied passing through the upper electrode within the chamber in conjunction with the wafer being placed at the lower electrode. At this time, the reaction product reached on the upper electrode during the etching process is solidified onto the adhesive layer. In other words, the reaction product deposits in the condition having a high degree of adhesiveness onto the adhesive layer formed on the surface of the upper electrode. Therefore, the exfoliation of the reaction product becomes more difficult and the generation of particles can be suppressed.
Further, an adhesive layer is formed on the upper electrode on which the reaction product is adhered. By so doing, the exfoliation of reaction product from the upper electrode can be prevented because the reaction product already adhered to the upper electrode is interposed between the adhesive layers and the reaction product generated by the subsequent etching process is adhered onto the newly formed adhesive layer. As the result, the generation of particles can be suppressed. In other words, a lamination layer structure is formed in which an adhesive layer and a reaction product are formed (adhered) alternatively on the surface of the upper electrode opposing the wafer to be etched. In this way, the generation of the particles can be suppressed in the etching process.